Process of esterification



UNITED STATESPATENT OFFICE I ace-mos .raocsss or ns'rsamc i'non George. De Witt Graves, Wilmington, Del., assignor to E.- I. du Pont de Nemours & Company, a

K W 11, M, a corporation of Delaware No Appllcation August 4, 1933, Serial 10 Claims. (CL 280-106) -"Ihis invention relates to a process of esterifl- The above objects are accomplished according cation and, more particularly, relates to the esto the present invention by esterifying a comteriflcation of certain hydroxyl compounds by pound from the group consisting of monohydroxyl means of ketene. compounds, glycerol, glycol, and derivatives of It is well known that the compound ketene glycerol and glycol containing at least one hy- CH:=C=O, more properly known as carbodroxyl group, by contacting same with ketene in methene, will react under some conditions with the presence of catalytic amounts of a strong acid. certain hydroxyl compounds to give an ester con- It has been found that such esteriflcation cata-' taining the acetyl radical. As shown in United. lysts as sulfuric acid, para-toluenesulfonic acid,

19 States Patent 1,604,471 to D. A. Nightingale and and the like, greatly accelerate the rate of acety- United States Patent 1,685,220 to E. E. Middleton, lation of certain hydroxyl compounds with ketene. this'reactionhas been used for the production of These two catalysts are particularly efllcient in cellulose esters in the presence of a catalyst. It is the present process, but other strong acids, such further known that other hydrox'yl compounds as chlorosulfonic acid, benzenesulionic acid, hy-

will react'with ketene to give esters, although drogen chloride, perchloric acid, phosphoric acids, 15 such reactions in the presence of an acid catalyst and the like, may also be employed to good adhave not been'carried out, to applicant's knowl-. vantage in the present process. It is very desiredge. The uncatalyzed reactions have been exable for the success of the process that the hytremely slow as a rule, in some cases so slow that droxyl compound. chosen be a liquid at room tem-' go apparently it was erroneously assumed that no perature or readily llquefiable (melting for exreaction at all took place. 1"he speed of these ample below 50 C.) in order to promote uniform uncatalyzed reactions decreases as one proceeds and intimate. contact between the catalyst, the

fromprimary to secondary to tertiary alcohols to ketene, and the hydroxyl compound. Some degree phenols. of acetylation can however be obtained by dis- 'Ketene is commonly produced by the pyrolysis solving (not suspending) the'hydroxyl compound, l

of acetone, 9. process which gives a gaseous mixif high melting, in an anhydrous solvent which? ture containing ketene, methane, and small is non-reactive to ketene, e. g. acetone, amounts of carbon monoxide, ethylene, and other The following examples are given to illustrate gases. Ketene cannot readily be prepared in the specific embodiments of the present invention.

pure state. It is therefore commonly utilized by In these examples the ketene used was in the 30 passing the gaseous mixturethrough the material ordinary mixture of gases obtained by cracking to' be treated, either in the pure state or disacetone to produce ketene, the ketene amounting solved or suspendedin a suitable inert medium. to about 25-50% of the gas mixture by weight.

Obviously the speed eillciency with which Gaseous mixtures containing different amounts ketene will be absorbed from the gaseous mixture ofketene can of course be used. 35 depends upon the reactivity of the compound Example 1.--Ketene gas was passed at the rate being treated. Rapid and complete absorption of of 2 grams" per minute through 4'? grams of k e makes for simplicity o rp n equilimelted phenol for three hoins. The phenol was ment and for high yieldsbased on the ketene it- 50% aoe y A 811111191 11111 made in 9 40, If the y i n 1 slow. it must be ca'rence of one gram of concentrated sulfufleacid 4'0 ried outin successive stages, or the ketene not resulted in the acetylation of phenol to the extent utilized in the primary reaction must be absorbed of 92.93% n 5 ham-a 1 in some more reactive liquid such as acetic acid, gm z 13 of primary whereby acetic anhydride would be produced as a aliphatic alcohols m by hydrogenatmg occur 41 mmduct- 1 nut oil acids. Ketene gas was passed at the rate 45 An object of the present invention is to provide a process whereby the esteriiication of monobyg wfii giz rgg g #:2 52 m g? vdroxyl compounds, glycerol, glycol, and derlvatum r from to i C 1% minutw tlves of glycerol and glycol containing at least to in mm f 18 minutes one hydroxyl group can belexpeditiously esteri- 1 3 i F'l nee by ketene. A further object is to provide a t time the m gained 3 grams we 8 process whereby the esteriflcation can be carried A 5111111991 1" in the Presence of out with rapid and complete absorption of the 1% w nesulfonlc a id, 3 grams of ketene. Other objects of the invention will be Lauro tr 4 stems i minutes- T 55 apparent from the description given hereinafter. temperature rose from 68 to83 C. in 4.5 min- 55 (iii) utes, where it was held for the remainder of the of Laurel gaining 19 grams in 18 minutes. The

temperature rose from 68 to 83 C. in three minutes, where it was held for the remainder of the period.

These three similar runs show clearly the efiect of the two catalysts on the rate of acetylation of Laurol.

Example 3. -Ketene gas was passed at the rate of 2 grams per minute through 166 grams of C. P. glycerol for 7.5 hours. The saponiiication number of the product was only 177.5, whereas the calculated values for the monoacetate and diacetate are 415 and 694, respectively.

In a similar run, 31 grams of glycerol, plus 10 drops of concentrated sulfuric acid, were treated with ketene gas for one hour. The saponification number of the product indicated 93% conversion todiacetate.

Example 4.--Ethyl ricinoleate (0.1' mol) was treated with ketene gas at the rate of 2 grams per minute for 8 minutes. Ihe temperature rose from 72 to 89 C. The gain in weight was 2.7 grams.

In a similar run, in the presence of 1% of concentrated sulfuric acid, 0.1 mol of ethyl rlcinoleate absorbed 4.5 grams oi ketene in 8 minutes. The temperature rose from 72 to 89 C. in two minutes. It was held below 93 C. for the remainder of the period by means of a water bath.

It is to be understood that the above examples are merely illustrative, as the invention includes within its scope the acetylation of monohydroxyl compounds, glycerol, glycol, and derivatives of glycerol and glycol containing at least one hydroxyl group, by means of ketene in the presence of catalytic amounts of a strong acid. By the term strong acid as used in the claims is intended to be included the various acids disclosed, and equivalents thereoi. While it is not desired to be confined to theory, it is believed that the principle of the present discovery lies in the intermediate formation of mixed drides between the ketene and the strong acid catalyst, especially inorganic acids; this could not occur with a basic catalyst. Tins mixed anhydride is highly reactive towards those monohydroiryl compounds, such as phenols and aliphatic alcohols, which past eiiorts to acetylate with ketene in the absence of a. catalyst have been mostly unsuccessful. In the subsequent esterification. with the mixed anhydride, the acetyl portion oi the anhydride reacts to form the acetate and the strong inorganic acid is regenerated for the iotion of more mixed anhydride. For this maction to proceed smoothly, and for the proper hution of the catalyst throughout the compound to be'acetylated, it is necessary to have that intimate contact which is obtainable only with liquid or readily liquefiable bodies; starches, carbohydrates, and celluloses do not fit these requirements, nor indeed is this same intimate contact obtained by suspending them in an inert medium. Certain higher-melting phenols and alcohols, e. g., diphenylolpropane, hydroirydiphenyls, resorcinol, pentaerytin'itoi, etc. can be employed with some success by dissolving them in an inert solvent medium such as acetone, hydrocarbons, etc. I 'his variation of the process cannot be applied to starches, celluloses and the like, since they are insoluble.

Other monohydroxyl compounds particularly suitable to be acetylated according to the present process include the monohydric aliphatic alcohols, hydroxy acids, hydroxy aldehydes, hydroxy esters, and hydroxy ketones; monohydric aromatic alcohols, and the ether-alcohols of glycerol and glycol, such as monoand di-ethylin, monoand di-methylin, methoxyand ethoxyethyl alcohol, and the like. Acetylations of other liqueflable hydroxyl compounds are also accelerated by strong catalysts, but less so than the above; among the types of compounds where the use of strong catalysts is less efilcacious, but nevertheless definite are polyhydric phenols, phenol alcohols, polyhydric alcohols other than glycerol and the glycols, and aliphatic Ref/ones, aldehydes, acids, etc., substituted by more than one hydroxyl group. Specific examples of the better types of monohydroxy compounds, which may be used alone or mixed, are: Methyl, butyl, lauryl, stearyl, crotyl, oleyl, geranyl, benzyl, xylenyl, cinnamyl, salicyl, cyclohexyl, menthyl, fenchyl, and tetrahydroturfuryl alcohols; ethylene glycol, butylene glycol, diethylene glycol, glycerol and polyglycola and polyglycerols; monoand di-aliryl, aryl and aralkyl ethers of glycerol, as the monobenzyl, monophenyl, and diethyl ethers; monohydric ether-alcohols such as ethoxyethyl, butoxyethyl, phenoxyethyl, p-methoxybenzyl, etc.; phenols such as phenol, the cresols, the xylenols, resorcinol mono methyl ether, thymol, eugenol, diphenylolpropane (in acetone solution); and

miscellaneous types such as ethylene glycoltion deals with acetylations with combo-methane,-

ketenes generally may be used. Among others which are suitable are:

Common name Iormula Methyiketcne-.- CH;CH=C=O- Ethyl eteno-..- CaHrOH=C= Dimcthyl ketone- ECH1hC=C=O Diphenylketcne CtH; :=C=0- Diphenylene ketcno (Cu =0:

Suitable ketenes have the general formula where R is gen or a hydrocarbon radical. However, the general instability and erratic behavior oi the substituted hetenes renders their use a definitely less preferred embodiment of the invention.

0f the catalysts disclosed, sulfuric acid and para-toluenesulronic acid are particularly emcacious in accelerating acetylation. However, the reaction may also be accelerated by other strong acids such as disclosed above. its is general in the use oi. catalysts, the amount required is exceedingly small, although larger amounts may be present without causing any harmful effect. It is preferred that the catalyst should amount to from 0.5% to 2.0% by weight of the hydroxyl compound being treated, although quantities outside this range are by no means precluded.

According to the process herein described, varibe used in a practical manner in many reactions which heretofore had never been considered more than experimental curiosities.

While the present invention has been described with particular reference to the acetylation of certain hydroxyl compounds by means of ketene in the usual mixture of gases obtained by the pyrolysis of acetone, it will be understood by those skilled in the art that the present invention is applicable to acetylation of these hydroxyl compounds with ketene gas either in the pure state or in admixture with a wide variety of other gases, particularly inert ones, such as nitrogen, methane hydrocarbons, carbon dioxide, unchanged acetone, etc.

As many apparently widely diiferent embodiments of this invention may be made without departing from the spirit and scope .thereof, it is to be understood that the invention is not limited .to the specific embodiments thereof except as defined in the appended claims.

I claim:

1. Process comprising esterifying a compound from the group consisting of monohydric COH compounds, glycerol, glycol, and derivatives of glycerol and glycol containing at least one hydroxyl group by contacting same with a ketene in the presence of catalytic amounts of a strong acid.

2. Process comprising esterifying a compound from the group consisting of monohydric COH compounds, glycerol, glycol, and derivatives of glycerol and glycol containing at least one hydroxyl group, by contacting same with a ketene in the presence of catalytic amounts of a catalyst from the group consisting of sulfuric acid and para-toluenesulfonic-acid.

3. Process comprising esterifying a compound from the group consisting of monohydric COH compounds, glycerol, glycol, and derivatives of glycerol and glycol containing at least one hydroxyl group, by contacting same with a ketene in the presence of from 0.5% to 2.0% by weight of concentrated sulfuric acid.

4. Process comprising acetylating a compound from the group consisting of monohydric COH compounds, glycerol, glycol, and derivatives of glycerol and'glycol containing at least one hydroxyl group, by passing a gaseous mixture containing carbo-methene into said compound in the presence of a catalytic amount of a strong acid.

5. Process comprising acetylating a compound from the group consisting of monohydric COH compounds, glycerol, glycol, and derivatives" of glycerol and glycol containing at least one bydroxyl group, by passing a gaseous mixture containing carbo-methene into said compound in the presence of catalytic amounts ofa catalyst from the group consisting of sulfuric acid and para-toluene sulfonic acid.

6. Process comprising acetylating a compound from the group consisting of monohydric COH compounds, glycerol, glycol, and derivatives of glycerol and glycol containing at least one hydroxyl group, by passing a gaseous mixture containing carbo-methene into said compound in the presence of from 0.5% to 2.0% by weight concentrated sulfuric acid.

7. A process for acetylating a liqueflable hy-- droxyl compound wherein the hydroxyl radical is directly attached to carbon which comprises pass,- ing a gaseous mixture containing carbo-methene into said compound in the presence of a catalytic amount of a strong acid.

8. A process for acetylating a liquefiable hydroxyl compound wherein the hydroxyl radical is directly attached to carbon which comprises passing a gaseous mixture containing carbo-methene into saidcompound in the presence of a catalytic amount of a strong inorganic acid whichpromotes said acetylation by the intermediate formation of a mixed anhydride and subsequent decomposition thereof.

' 9. A process for acetylating, a liquefiable hydroxyl compound wherein the hydroxyl radical is directly attached to carbon which comprises passing a gaseous mixture containing carbomethene into said compound in the presence of catalytic amounts of a strong acid and of a solvent for the hydroxyl compound, said solvent being non-reactive toward carbo-methene.

10. A process for acetylating a hydroxyl compound wherein the hydroxyl radical is directly attached to carbon which is a liquid below C. which comprises passing a gaseous mixture containing carbo-methene into said compound in the presence of a strong acid catalyst.

GEORGE DE GRAVES. 

